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Superplastic forming
Grycz, Radek ; Lidmila, Zdeněk (referee) ; Peterková, Eva (advisor)
This work is focused on description of behavior of superplastic materials and methods of sheet forming of these materials. Lists the advantages and difficulties in using this method and examples of products made by this procedure.
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Superplastic deformation of ultrafine-grained magnesium alloys containing rare earth metals and zinc
Vávra, Tomáš ; Minárik, Peter (advisor) ; Čížek, Jakub (referee)
Superplastic behavior of two ultrafine-grained (UFG) magnesium alloys was investigated in this thesis. Commercial Mg-4Y-3RE (wt.%) alloy was prepared by equal channel angular pressing (ECAP) and new experimental alloy Mg-23Zn-2Y (wt.%) was prepared by extrusion and ECAP. Eight passes of Mg-4Y-3RE through ECAP resulted in grain refinement down to ~340 nm and formation of a high volume fraction of fine secondary phase particles. UFG microstructure with an average grain size of 3.2 µm after extrusion and 1.6 µm after Ex-ECAP was achieved in Mg-23Zn-2Y alloy. The microstructure of Mg-23Zn- 2Y was observed by scanning and transmission electron microscopy. The thermal stability of both alloys was measured by microhardness tests. Superplastic behavior was investigated in the temperature range of 250-450 řC and strain rate range of 5x10-4 s-1 - 10-1 s-1 . The results revealed a high strain rate superplasticity in Mg-4Y-3RE alloy. Deformation to fracture exceeded 1000% for several deformation conditions, even at the strain rate of 10-1 s-1 . The highest elongation of 656 % in Mg-23Zn-2Y alloy was achieved in extruded state at the strain rate of 10-3 s-1 .
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Superplastic deformation of ultrafine-grained magnesium alloys with potential for use in medicine
Vávra, Tomáš ; Minárik, Peter (advisor) ; Málek, Přemysl (referee)
Mechanical properties of ultra-fine grain magnesium alloys AE42 and LAE442 prepared by ECAP were investigated. The study was focused on finding suitable conditions for the superplastic deformation. In the first place, the thermal stability of the microstructure was investigated. Afterwards, the strain rate sensitivity was measured in the temperature range 180-240 řC and the strain rate of =5·10-5 -2·10-3 s-1 . Conditions for tensile tests of =10-4 s-1 at 180 ř C and =10-3 s-1 at 240 řC ware selected. Finally, the microstructure change as a result of deformation was observed by AFM and EBSD. The results were discussed with mechanical tests. The best superplastic properties were observed in LAE442 alloy deformed at 180 ř C and =10-4 s-1 . Under these conditions, the achieved tensile strain was 395%.
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Mechanical properties of ultrafine-grained magnesium alloys
Nováková, Helena ; Stráská, Jitka (advisor) ; Král, Robert (referee)
This work is focused on the mechanical properties of ultrafine-grained magnesium alloy AZ31 prepared by EX-ECAP method. The main goal of the bachelor thesis is to find external conditions of superplastic deformation: deformation temperature (measured in the range 150 řC - 350 řC) and strain rate (measured in the range 10-5 s-1 - 10-2 s-1 ). Properties related to the mechanisms of superplasticity (strain rate sensitivity parameter, maximum stress and maximum elongation) were evaluated. Deformation mechanisms were furthermore observed using atomic force microscopy.
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Superplastic forming
Grycz, Radek ; Lidmila, Zdeněk (referee) ; Peterková, Eva (advisor)
This work is focused on description of behavior of superplastic materials and methods of sheet forming of these materials. Lists the advantages and difficulties in using this method and examples of products made by this procedure.
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